1. Field of the Invention
The present invention relates generally to a retainer for accurately positioning and retaining components.
2. Problem to be Solved
(i) Background and Long-Felt Need
During the manufacture of electronic components, it is sometimes necessary to hold or retain the components as they are processed in one or more operations. In many instances, these operations require light or no contact with the component, such as photographic processing and inspection, laser trimming and machining, and component testing. Another example is screen-printing of many small-sized, identical substrate pieces with identical microelectronic patterns. These patterns must be accurately placed on the substrate pieces within predetermined tolerances. Furthermore, it is essential that the substrate pieces are not scratched, chipped or damaged, or chemically contaminated with foreign particles. Such damage can occur through abrasion or other undesirable contact. Therefore, in many of the aforementioned operations, the component or substrate pieces must be accurately held in the X, Y and Z dimensions within predetermined tolerances. Typically, these tolerances are about 0.001 inch (1 mil). What is needed is a component retainer that can accurately position and retain a substrate piece or component in the X, Y and Z dimensions within tolerances of about 0.001 inch. Furthermore, such a component retainer must be capable of retaining planar components in a manner such that the planar components are flush with the component retainer surface so as to prevent excessive contact between the component and screen-printing equipment. Additionally, it is also essential that such a component retainer can be manufactured at reasonable costs.
(ii) Failure of Others
There have been many attempts to solve the aforementioned problems associated with accurately positioning and retaining components or substrate pieces. One such attempt is the device disclosed in U.S. Pat. No. 5,133,939 (the "'939 patent") which utilizes an elastomeric material, such as rubber, tensively configured completely around the component. The device of the '939 patent is suitable only for retaining cylindrical shaped components and cannot be used to retain components having a planar geometry because it would be difficult to mount the component in the stretched rubber. Furthermore, the stretched rubber is not capable of holding planar-geometry components at constant positions due to the twisting action produced by the rubber. Such twisting action results in the components being retained at random positions that depend on where the components originally engaged the rubber. Additionally, the device of the '939 patent does not preclude movement of the substrate piece or component in the "Z" axis. Furthermore, the device of the '939 patent does not allow for selective modification of the compliance of the rubber in order to bias the component to a specific orientation. Another attempt to solve the aforementioned problems is found in U.S. Pat. No. 5,007,534 (the '534 patent) which discloses a retainer formed in a rigid metal plate wherein an elastic material is used to retain the components. Only elastic material exists between the retaining holes. There is no frame material between the elastically held components. It has been found that the device of the '534 patent does not exhibit the required accuracy in the placement of the component. This would be evident for example, if oversized parts were placed starting at one end, resulting in the distorted positions of adjacent parts due to the accumulated displacement of the compliant material. Additionally, it would be difficult to process components which vary significantly in size. Since a relatively non-compliant material would be necessary to accurately locate the component, the ability to accommodate relatively large size variations would be precluded. A further attempt to solve the aforementioned problems is found in U.S. Pat. No. 4,928,821 (the '821 patent) which discloses a fixture for holding electronic components using an elastomeric material that grasps the sides of the component. When the components are inserted into the fixture of the '821 patent, they are forced through and held in place by the gripping action of the tensively configured elastomeric material against the sides of the component. However, the fixture of the '821 patent cannot hold components flush with the fixture surface. Furthermore, the fixture of the '821 patent cannot hold components accurately in the X, Y or Z axis. Additionally, it would be difficult to accurately machine openings in the elastomeric material used in the '821 patent in part because the elastomeric material is on both outer surfaces of the base plate. This would require separate machining steps on each side. Otherwise, the openings in the elastomeric material layer must be formed before the elastomeric material is attached to the base plate. Other conventional component retaining apparatuses utilize synthetic resins in forming a retaining fixture. However, it is difficult to process synthetic resins to obtain a uniform thickness over the entire area of the synthetic resin layer.
(iii) Objects of the Present Invention
Bearing in mind the problems and deficiencies in conventional retainers, it is an object of the present invention to provide a new and improved component retainer that can accurately position and retain a component in a predetermined position.
It is another object of the present invention to provide a new and improved component retainer that may be utilized with components having a planar geometry and which have a thickness substantially the same as the thickness of the component retainer.
It is a further object of the present invention to provide a new and improved component retainer that substantially reduces excessive component movement in the "Z" axis.
It is another object of the present invention to provide a new and improved component retainer that may be utilized with components of various sizes, or with components with fairly large variations above or below a given nominal size.
It is yet a further object of the present invention to provide a new and improved component retainer that can be manufactured and implemented at a reasonable cost.
Other objects and advantages of the component retainer of the present invention will be apparent to one skilled in the art in light of the ensuing description.